The Hypertension Prevention Trial (HPT) is a multicenter randomized clinical trial, designed to test the feasibility of preventing the development of hypertension by dietary measures. The centers in the trial include: Four Clinics, a Data Coordinating Center, a Nutrition and Education Resources Center, a Food Coding Center, a Central Laboratory, and a Project Office. A total of 841 men and women (919 including the test cohort) with qualifying diastolic blood pressure greater than or equal to 78 mmHg but less than 90 mmHg and ages 25 through 49 at entry were recruited by the four clinical centers over a thirteen month period ending September 30, 1983. The 841 participants were randomly assigned to a control treatment (Ct: No dietary treatment), or to one of four treatments with the goals of: . Na: Reducing dietary sodium to less than or equal to 70 mEq/day . Nak: Reducing dietary sodium to less than or equal to 70 mEq/day and increasing dietary potassium to greater than or equal to 100 mEq/day . NaCal: Reducing dietary sodium to less than or equal to 70 mEq/day and reducing caloric intake to a level designed to reduce body weight to a "normal" level . Cal: Reducing caloric intake to a level designed to reduce body weight to a "normal" level Funding is requested for continued treatment and semi-annual follow-up data collection visits in order to detect differences in blood pressure changes over a time period appropriate to the natural course of the development of hypertension, and for data analyses and paper writing. Results to date indicate that it is possible to effect and sustain dietary changes. The effect of those changes on blood pressure is the focus of the study.